The present invention relates in general to magnetic head assemblies for rotating disk drives, and particularly, to head assemblies having a leading edge step scheme for tuned air entrainment.
Disk drives of the type that receive data storage media typically have a head assembly for communicating with the storage medium. The data storage cartridge may be of the type that is removable from the disk drive. The storage medium may be disk shaped, and if so, the data storage cartridge may be referred to as a disk cartridge. The head assembly may include a pair of sliders. Each slider is typically mounted on an actuator that is mounted within a disk drive. Additionally, each of the sliders may have a read/write sensor(s) for interfacing with a storage medium of a disk cartridge. The sliders are also commonly referred to as read/write heads.
Generally, the actuator on which the head assembly is mounted moves between a retracted position and an interfacing position. In the retracted position, the heads are disposed in a position that minimizes the likelihood of damage to the heads from either dynamic or static forces. When a disk cartridge has not been inserted into the disk drive, the actuator holds the heads in this retracted position. When a disk cartridge is inserted into the disk drive, the actuator moves the heads to the interfacing position. In the interfacing position, the actuator is in a position in which the heads can interface with the storage medium that has been inserted into the disk drive.
The storage medium with which the head assembly may interface may have a top surface and a bottom surface. Preferably, in the interacting position the storage medium is disposed between the sliders of the head assembly. One of the sliders may be disposed proximal to the top surface, and one of the sliders may be disposed proximal to the bottom surface. In operation, the storage medium of the disk cartridge is rotated between the sliders and an air bearing is created between the storage medium and each of the sliders. As the storage medium is rotated, the storage medium xe2x80x9cridesxe2x80x9d on this air bearing and the heads interface with the storage medium.
The design of head assemblies is significant because it affects the ability of the heads to interface with the storage medium of the disk drive. In particular, the ability of the heads to interface with the storage medium is a function of the spacing between the sliders and the storage medium. The spacing between the sliders and the media is important because it affects the ability of the disk drive to communicate with the media. Ordinarily, the sliders fly very low with respect to the media, and in some instances, such as with flexible media, a portion of the sliders may contact the media. As the distance between the media and the sliders increases, the signal degrades. With the development of higher density media, it is desired to develop sliders that have even lower fly heights than those previously developed.
For instance, one of the concerns when designing head assemblies is that the spacing between the read/write heads and the storage medium be relatively constant. If the spacing between the read/write heads and the storage medium is not relatively constant, this can cause a degradation in the ability of the heads to interface with the storage medium. The importance of maintaining the spacing between the storage medium and the heads relatively constant is even, more pronounced in disk cartridges that have storage mediums with a relatively high density.
In order to maintain an appropriate spacing between the read/write heads and the storage medium, the air bearing created between the slider and the storage medium should be relatively constant. At high speeds, the flexible storage medium tends to flutter and therefore the importance of maintaining the spacing between the read/write heads and the storage medium is even more pronounced at high speeds. In addition to being dependent on the speed of rotation of the storage medium, the air bearing is a function of the geometry of the head assemblies and the storage medium. Therefore, the geometry of these components is of particular importance.
Slider performance can be measured using several parameters. For example, one important parameter is the xe2x80x9cfly height,xe2x80x9d which is the distance between the magnetic transducer on the read-write head and the magnetic layer on the disk. Another important parameter is xe2x80x9croll,xe2x80x9d which is the difference between the distance between the inside rail and the disk surface and the distance between the outside rail and the disk surface while the read-write head is flying over the disk. Another important parameter is xe2x80x9cpitch,xe2x80x9d which is the difference between the distance between the leading edge and the disk surface and the distance between the trailing edge and the disk surface while the read-write head is flying over the disk.
A class of conventional sliders are sliders which include a leading edge, a trailing edge, first and second side edges, first and second raised side rails positioned along first and second side edges, respectively, and leading edge tapers for facilitating a flow of air under the side rails during takeoff and for helping to maintain an air bearing under the slider as it flies over the surface of the disk. In this regard, reference is made to U.S. Pat. Nos. 5,831,791 and 5,949,614, both issued to Chhabra (U.S. Pat. No. 5,949,614 is a continuation of U.S. Pat. No. 5,831,791). These patents show and describe an Adjustable Negative Pressure Air Bearing (NPAB) Slider which provides means for controlling the slider characteristics including roll, pitch, fly height, and skew sensitivity. The NPAB slider controls the flying characteristics of the slider by providing a positive pressure, negative pressure, and transition regions whereby the shape of the regions determines the direction and amount of air flowing into the negative pressure region and thus the magnitude and distribution of negative pressure generated. One embodiment of the slider disclosed has side rails with tapered leading edges, and another embodiment includes side rails with leading edge steps.
For high capacity flexible magnetic recording technology, it is desired that there be contact between the flexible media and the part of the head where the sensor is located. The balance of the head should fly over the flexible media in order to maximize the amount of data that can be stored to and read from the surface of a disk.
In addition to affecting the performance of the head assembly, the spacing between the head assembly and the storage medium also affects the life of both the read/write heads and the storage medium. For instance, if the storage medium fluctuates, the storage medium and the heads may wear unevenly and their respective lives may be reduced. Furthermore, if the air bearing pressure is relatively high, the storage medium and the heads will wear at a faster rate. The amount of fluctuation of the storage medium is a function of a large number of variables, including, for example, the geometry of the head assembly and the storage medium, the cartridge shell, rotational velocity, the media mechanical properties (e.g., size, thickness, substrate material, etc.), and the like. Manufacturing imperfections in head assemblies and/or variations in drives and head assemblies due to large design tolerances have the potential to cause an imbalance of forces between the head assembly and the storage medium and subsequent fluctuations of the storage medium. Accordingly, it is important to design head assemblies, so that the manufacturing tolerances are relatively low and the likelihood of manufacturing imperfections is reduced.
In addition, although it is preferred to have leading edge tapers that are machined, modem manufacturing techniques for higher capacity heads/sensors only support heads that are etched, not machined. As a result, it is necessary to develop improved leading edge steps instead of ramps.
Therefore, a need exists for head assemblies having a leading edge step scheme for tuned air entrainment to improve the performance of the head assemblies for higher speed and higher density applications. This invention includes improved head assemblies for disk drives. This invention also includes disk drives and disk drive actuators that employ the improved head assemblies of this invention.
According to this invention, an improved head assembly has a first and a second slider for interfacing with a data storage medium of a data storage cartridge. The second slider is preferably disposed below the first slider. The data storage cartridge with which the head assembly of this invention may be employed may be a disk cartridge of the type that can be inserted and ejected from a disk drive. However, the head assembly of this invention may be employed with other types of data storage drives. The head assembly may be a magnetic head assembly and be employed with a magnetic data storage media. However, the head assembly of this invention is not so limited and may be employed with other types of data storage media, such as, optical media. Moreover, the head assembly of this invention may be employed with a variety of types of disk drives, such as, a scanner disk drive, a camera disk drive and a computer disk drive. These examples are not intended to be limiting.
The tuned leading edge step scheme of the present invention relates to a pair of opposed sliders having a tuned leading edge step scheme wherein an air bearing generated under each rail of the slider can be adjusted by controlling the air entrainment characteristics of the first and second longitudinal rails to obtain desired slider flying characteristics. The improved head assembly includes a first and a second slider that each have a first and a second longitudinal rail. These rails preferably extend parallel to the longitudinal axis of the respective slider. Both the first and the second sliders have a tuned leading edge step scheme that comprises one bleed leading edge step and one structured leading edge step formed in the first and the second longitudinal rails, respectively.
The bleed leading edge step is relatively poor at entraining air due to its construction which allows air to bleed out of the step area. This results in a relatively poor air bearing being formed under the first rail. In one embodiment, the bleed leading edge step can include a plain leading edge step. In another embodiment, the bleed leading edge step can include a bleed structure formed as a portion of the first longitudinal end of the first rail and extending into the bleed leading edge step. The bleed structure extends into the bleed leading edge steps to facilitate a flow of air out of a region between the storage medium and the bleed leading edge step thereby further reducing air entrainment. The bleed structure can include, for example, a rectangular shape, a square shape, a triangular shape, a curved convex shape, a semi-circle shape, a semi-oval shape, etc. The bleed structure may extend to the leading edge of the slider, or alternatively, the bleed structure may terminate before reaching the leading edge.
In another embodiment within the scope of the present invention, the bleed leading edge step can include partial air dams and bleed slots formed along the first and second longitudinal sides of the first rail. The partial air dams may extend a predetermined distance from the leading edge toward the trailing edge of the slider. The bleed slots are defined by a trailing edge of the partial air dams and the first longitudinal ends of the first rail. The bleed slots allow a portion of air entrained in the bleed leading edge step to bleed out of the bleed leading edge step thereby reducing air entrainment by the bleed leading edge step.
The structured leading edge step is formed having a pair of air dams disposed longitudinally along the sides of the structured step and is relatively good at entraining air due to its construction having the air dams. This results in a relatively good (e.g., robust) air bearing being formed under the second rail. This tuned leading edge step scheme wherein one rail having a sensor being relatively poor at entraining air and the other rail not having a sensor being relatively good at entraining air, forces the storage medium to comply in an advantageous manner (e.g., conform) to cause intimacy at the sensor.
The sliders may be disposed in the disk drive such that the longitudinal rails of each of the sliders are aligned. Preferably the first longitudinal rail having a bleed leading edge step of each of the sliders is aligned with the second longitudinal rail having a structured leading edge step of the other slider. As described, a storage media may be disposed between the sliders.
Each slider of the head assembly can be formed having one leading edge step constructed differently from the other leading edge step. In addition, the shape and dimensions of the leading edge steps can be varied to control the flying characteristics of the head assemblies.
Each of the sliders preferably may have a magnetic read/write sensor disposed on an end of each of its longitudinal rails. The sensor may be disposed in the first longitudinal rail that has the bleed leading edge step. Through this sensor the head assembly can communicate with a microprocessor. In a preferred embodiment, the head assembly is a magnetic head assembly that has an electromagnetic sensor for communicating with a magnetic data storage media.
Each of the sliders preferably has a leading edge and a trailing edge. The leading edge is that which leads the sliders into the direction of rotation of the storage medium, and the trailing edge is that which trails the direction of motion. The sensor is preferably disposed proximal to the trailing edge of the sliders.
The head assembly of this invention may be disposed on an actuator within a disk drive. In a preferred embodiment of this invention, the head assembly is disposed on a rotary type of actuator, and in an alternative preferred embodiment the head assembly is disposed on a linear type of actuator. The actuator is preferably moveable between a retracted position and an interfacing position. In the retracted position, the head assembly is retracted relative to the area in which the disk cartridge rests within the disk drive when the disk cartridge is inserted into the disk drive. When a disk cartridge is inserted into the disk drive, the actuator may be moved to the interfacing position. In the interfacing position, the head assembly of the actuator is disposed proximal to the storage medium of the disk drive. More particularly, the storage medium may be disposed between the first and the second slider, so that the first slider is disposed proximal to a first surface of the storage medium and the second slider is disposed proximal to a second surface of the storage medium.
The storage medium is preferably rotated as it is positioned between the first and the second slider. As the storage medium rotates, hydrodynamic pressures are created between the first surface of the storage medium and the first slider and the second surface of the storage medium and the second slider. These hydrodynamic pressures are the air bearings between the first surface of the storage medium and the first slider and the second surface of the storage medium and the second slider.
Because of the tuned leading edge step scheme in the longitudinal rails of the sliders, air is bled from the area that is proximal to the bleed leading edge step between the first surface of the storage medium and the first slider and the second surface of the storage medium and the second slider. By bleeding air from these areas, an area of relatively low pressure is created in the area that is proximal to the bleed leading edge steps. In effect, the air bearing is essentially minimized or starved by the bleed leading edge steps. At the same time, air is being entrained by the air dams of the structured leading edge step. As a result, the entrained air of the structured leading edge step forms a relatively high pressure in the area that is proximal to the structured leading edge step and under the second rail. Because of the area of relatively high pressure being opposed by an area of relatively low pressure, the storage medium deflects toward the first rail having the bleed leading edge step and the sensor. The tuned leading edge step scheme forces the flexible media to deflect in an advantageous manner to cause intimacy (e.g., contact) at the sensor. That is the storage medium is deflected upward toward the first longitudinal rail having a sensor of the first slider and downward toward the first longitudinal rail having a sensor of the second slider. Since, as described above, the sensor is disposed proximal to the trailing edge of the first longitudinal rails of the sliders, the storage medium deflects toward the sensor in each slider. The storage medium may even deflect so as to drag or contact the trailing edge of the first longitudinal rail where the sensor is located. By deflecting the storage medium toward the sensors, the performance of the head assembly is enhanced. Other advantages described below may also be achieved by deflecting the storage medium with the tuned leading edge step scheme comprising a bleed leading edge step and a structured leading edge step in each slider.
In a preferred embodiment, the head assembly is a magnetic head assembly that interfaces with a magnetic data storage media. The head assembly may also be used for optical communication with optical data storage media.
The foregoing and other aspects of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.